Solar flux is the spectral irradiance received by the Earth's surface from the sun, measured in W·m−2·Hz−1. It is used as a basic indicator of solar activity and can therefore be used to guide installation choices of photovoltaic solar panels. Photovoltaic solar panels use light energy from the sun to generate electricity. Solar flux is typically affected by various factors—orientation of the roof relative to the sun, angle of the roof, roof shape and obstacles, shadows cast by trees and other buildings, seasonal weather patterns, etc. Solar flux has typically been presented in static, two-dimensional (2D) forms; for example, using a color gradient to represent a snapshot of solar power on the roofs of buildings on a map.